1. Field of the Invention
The present invention relates a digital communication system, and more particularly, to a system for a digital television (DTV) transmitter/receiver and a method of coding main and enhanced data in the DTV transmitter/receiver. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for transmitting and receiving digital broadcasts by VSB (vestigial side bend).
2. Discussion of the Related Art
Generally, the 8T-VSB transmission system adopted as a digital broadcasting standard by Korea and North America is a digital broadcast system developed for MPEG video/audio data transmission.
As the digital signal processing technology rapidly develops with the global use of Internet, the tendency for combining digital home appliances, computer and Internet together rises. So, in order to meet the user's various demands, many efforts need to be made to develop a system capable of transmitting various supplemental data with video/audio data.
A user of supplemental data broadcasting is expected to use the supplemental data broadcasting using a PC card or portable device having a simple type indoor antenna attached thereto.
Yet, signal intensity can be considerably decreased due to a shield effect of a wall and an Influence of a near moving object within an indoor space and broadcast receiving performance can be reduced due to a ghost and noise generated from a reflective wave. Unlike a case of general video/audio data, a case of supplemental data transmission should have a lower error rate. In case of the video/audio data, an error failing to be detected by human eyes/ears does not matter. Yet, in case of supplemental data (e.g., a program execution file, stock information, etc.), a 1-bit error can cause a serious problem. So, the demand for developing a system more persistent against ghost and noise generated from a channel rises.
Additional data transmission will be performed by time-division through the same channel of MPEG video/audio in general. Since the beginning of digital broadcasting, ATSC VSB digital broadcast receivers receiving the MPEG video/audio only have globally spread in markets. So, the supplemental data transmitted on the same channel of the MPEG video/audio should avoid causing any effect to the conventional ATSC VSB dedicated receiver previously supplied to the markets. Such a situation is defined as ATSC VSB compatibility. And, a supplemental data broadcast system should be compatible with the ATSC VSB system. Besides, the supplemental data could be called enhanced data or E-VSB data.
However, in a poor channel environment, reception performance of the conventional ATSC VSB reception system may be reduced. Specifically, a portable or mobile receiver needs higher robustness against a channel change and noise.